Distribution and Biology of Blue Hake (Antimora rostrata Gunther 1878) in the Northwest Atlantic with Comparison to Adjacent Areas

Abstract

Blue hake (Antimora rostrata) is a globally distributed species found in most slope waters around the world Based on commercial fisheries data (it was found to be a common bycatch) and research survey records, this study examines the distribution and aspects of the biology of blue hake in Can adian waters. It forms a continuous distribution in slope waters from the US/Canada border in the south (contiguous with the distribution in US slope waters) to Arctic waters between Greenland and Baffin Island. In relation to depth, blue hake were found as shallow as 200 m but rare in less than 500 m. Only 9% of the survey sets containing blue hake occurred in less than 500 m but were most common in the deepest survey sets (1600 m). Longline sets from the 1960’s at 2000-2400 m revealed that blue hake were relatively common at those depths. Studies from other parts of the world found blue hake distributed as deep as about 3000 m. Numbers per tow increased with depth, peaking at 1400 m (although depths greater than 1400 m were poorly sampled). This compares with peak abundance observed at depth of about 1700 m in US waters. Catch rate increased at a faster rate with depth in the southern part of our study area. With respect to temperature, sets with blue hake spanned a range of bottom temperatures between 0.9 and 8.7°C. However, only 1% of the survey sets with blue hake were associated with bottom temperatures less than 3°C and only 2% of the survey area was associated with bottom temperatures exceeding 3°C. This associated temperature range is similar to what has been observed in other parts of the world. Blue hake lengths were measured from sets of the deepwater commercial fisheries. The largest fish taken in Canadian waters were 65 cm. The smallest specimen was 5 cm although fish less than 22 cm were rare exc ept in longline catches in 1987 when fish in the range of 5-15 cm were not uncommon. An attempt to use otoliths to age blue hake revealed that many more rings than years appears to be the case. Studies in US waters to the south found no evidence of spawning and scant evidence of mature individuals and it was hypothesized that spawning took place to the north in Canadian waters. The current studies indicate this not to be the case. No eggs or larvae of this species have been found in the area studied (as is the case elsewhere) and very few individuals less than 10 cm have been taken in either survey or commercial gear. Individuals with maturing gonads were also rare. Fishing mortality due to by -catch of this species was estimated. Determining absolute biomass of this species in Canadian waters and thus the impact of fishing on the population was not possible since a substantial portion of its range (depths greater than 1500 m) are not sampled.